One type of harvester for grapes generally straddles a row of vines and either is driven or towed along the row to progressively harvest grapes along the row. The picking is effected by a picking head which includes opposing banks of picking rods supported on opposing sides of the row. The picking rods oscillate into and out of the vines, to grip and shake the vines so as to shake the grapes from the vines. The grapes that are removed, fall onto interleaved and pivotable collecting plates supported at a lower portion of the conveying frame which plates direct the grapes to a conveyor system, for carrying the grapes to a collection vessel such as a hopper. An example of type of harvester is disclosed in U.S. Pat. No. 4,944,387 by Burke.
A second type of harvester is frequently used in harvesting raisins because of the different shaped trellis support. Raisins are grown on specialised trellises that provide supporting surfaces that in alternate years are used for training new growth onto or for supporting cut vines to hang the drying raisins. Harvesters used for normal grape trellises are not effective at removing raisins from such raisin trellises because the growing surfaces are angled upwardly. In place of the opposing banks of picking rods, is a roller drum which can roll along the direction of the trellises, the roller drums including a great number of radially extending picking fingers. The roller drum is supported on a pivoting arm, the angle of the pivoting arm can be changed to support the roller drum to suit the trellis type. The striking force is effected by an oscillation movement being impacted axially onto the roller drum. This type of harvester is also used for harvesting other berries or grapes from other trellis arrangements.
In harvesters of the first type known to the inventor oscillatory movement is imparted onto the rods via a driving arm eccentrically connected to a driving shaft. Generally there is a separate driving shaft for each arm extending vertically on a respective side of the harvester and the two driven shafts are, together, driven by a common drive which is connected to a motor. These eccentric drives are positively connected to the picking rods.
This arrangement has several disadvantages. When driven under moderate load this direct coupling arrangement is adequate, however, invariably in order to get sufficient penetration into the vine canopy the harvesting head is driven relatively hard. Under these circumstances the unbalanced eccentrically weighted load has an adverse, wearing, effect on the drive mechanism.
Additionally direct coupling also has an adverse effect when an uneven load is applied between the two opposing banks of shaker rods and consequently the respective driven shafts, such as occurs at the ends of a row or when a bank (or roller) of picking rods contacts a strainer post or trellis cross arm.
Furthermore, it is difficult to achieve an appropriate balance between the force exerted by the picking rods, the amplitude of the stroke of the rods and the frequency of stroke. It is desirable to vary all three of these parameters so as to achieve an effective harvest yet minimise damage to the crop and trellis system. A combination of variation of these three parameters will give best results. In prio art machines the amplitude can vary as can the frequency of vibration, however increased force can only be achieved by increasing the amplitude or speed, and this often results in a balance that is less than desirable, especially given the limitation in speed of existing machines. In effect the means of adjusting the picking head for more power is to increase the amplitude, which imparts too great a force on the trellis system with consequent greater damage and hence increased cost of maintenance. Additionally there is also a greater risk of vine breakage which, if severe enough, will result in a decrease in yield in subsequent harvests.
Orlando et al in U.S. Pat. No. 4,286,426 and Orlando in U.S. Pat. No. 4,336,682 have suggested the use of a non-positive oscillatory drive mechanism in the form of eccentrically mounted weight on a fruit harvester. The suggested harvester comprises two solid striker bars each mounted to be positioned on opposing sides of the sides of the trunks of a vine on one of two calipers. A pair of eccentric weights are mounted one on a respective one of the two calipers to provide a sideways rocking motion of the harvester, so that the striker bars alternatively strike the trunks of the vine. The problem with this type of harvester is however that it is not as effective at harvesting because generally it is far better to the contact the grapes in a more direct fashion, and more evenly over the vine. The particular manner of contact with the vine is important and it is desirable to provide a high frequency contact with the vine as broadly as possible distributed over the vine.
Scudder in U.S. Pat. No. 4,283,906 suggests non-positively coupling out of balance weights to the top of a drum-type picking head. These eccentrics however, do not provide for an axial oscillatory component to the picking head but rather give a radial oscillatory component. The oscillatory movement of Scudder relates to penetration into the vine, rather than relating to a direct picking effect.
Windemuler et al in U.S. Pat. No. 529,177 also relates to a drum type picking head. This disclosure shows the coupling of an eccentric motor to the top of a shaft supporting a drum type picking head. The picking head is vibrated axially by the eccentric motor.